Detonator primer capsule

ABSTRACT

A detonator for detonation of explosives which provides protection of a primer charge from sympathetic initiation and provides efficient detonation of a base charge. The detonator is comprised of, a hollow detonator shell having first and second ends, said detonator shell has inserted therein a delay element and a primer capsule. Said delay element is positioned within the first end of the shell and has a core running therethrough. The primer capsule has a protective frustrum top having an opening centrally located therein and a tubular bottom. The primer capsule is inserted into the second end of the shell such that the core of the delay element is in contact with the opening in the frustrum top. The primer capsule top contains a primer charge and the bottom contains primer charge and a small amount of base charge material. The top is constructed with heavy walls such that the primer charge is protected. Further, the top is constructed such that upon initiation of the primer charge by the delay element the output of the primer charge is focused toward the base charge material which when initiated initiates an external base charge. The primer capsule construction provides a system wherein the primer charge reaches full velocity and shock by the time it reaches the small amount of base charge material and thus provides more efficient initiation.

TECHNICAL FIELD OF THE INVENTION

The invention relates to a detonator for explosives. Specifically, theinvention relates to a primer capsule for incorporation into a detonatorwhich is constructed such that a primer charge housed within the capsuleis protected from sympathetic initiation and the output from theinitiated primer charge is focused toward a small amount of base chargematerial contained within the capsule to provide efficient detonation ofan external base charge.

BACKGROUND OF THE INVENTION

The present invention relates to explosive detonators, and moreparticularly, relates to explosive detonators wherein the primer chargeis protected and the output of the primer charge is focused toward thebase charge providing efficient initiation.

There are various detonator designs known in the art which basicallyfall into three categories. The first category of detonators areconstructed such that the primer charge is located on top of the basecharge and in intimate contact with the delay element. These designs donot provide for protection of the primer charge against sympatheticdetonation, nor do those designs provide for focusing of the output fromthe primer charge for efficient detonation.

A second category of detonators known in the art are constructed suchthat the primer charge is protected in some manner, but includes a gapbetween the primer charge and the delay element, and thus, reliableinitiation is not obtained. Further, these designs do not provide ameans to focus the primer charge output toward the base charge and thus,are inefficient.

The third category of detonators known in the art are common amongEuropean manufacturers and are constructed such that the primer chargeis located inside the delay element which is in intimate contact withthe delay element core and protected against sympathetic detonation, butthese designs do not focus the primer charge output toward the basecharge and thus, are also inefficient.

None of the known detonator designs provide (1) primer charge protectionagainst sympathetic initiation, (2) focusing of the primer charge outputfor efficient base charge initiation, and (3) intimate contact betweenthe delay element and the primer charge for reliable initiation. Thepresent invention provides a detonator which supplies protection of theprimer charge, reliable initiation and efficient use of the primercharge and base charge materials.

SUMMARY OF THE INVENTION

The invention is directed to explosive detonators having a primercapsule contained therein. The primer capsule is comprised of a top andbottom. The capsule has a channel running therethrough wherein primercharge material and base charge material are contained. The capsule top,which is pointed in shape or frustrum shaped, contains primarily primercharge material in the channel. The top has an opening centrally locatedtherein which is in communication with the channel containing primercharge and base charge material. The top provides protection for theprimer charge against sympathetic detonation. The channel in the bottomwhich is in communication with the primer charge contained in the topcontains primer charge and a base charge material. The base chargematerial is less sensitive than the primer charge and is preferablypacked or pressed against the primer charge. The base charge materialprovides protection or insulation of the primer charge againstsympathetic initiation from forces directed from the bottom of theprimer capsule. The channel in the top and a portion of the channel inthe bottom are preferably frustro-conical or frustro-trapezoidal shapedand thus focuses the output of the primer charge toward the base chargematerial to provide efficient detonation of an external base material.Also, the entire channel, in the top and bottom, can be frustro-conicalor frustro-trapezoidal shaped.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of the primer capsule of the presentinvention;

FIG. 2 is a perspective view of the primer capsule of the presentinvention;

FIG. 3 is a cross-sectional view of the primer capsule of the presentinvention loaded with primer charge and a small charge of base material;

FIG. 4 is a cross-sectional view of the primer capsule of the presentinvention incorporated into a detonator shell;

FIG. 5 is a cross-sectional view of the primer capsule of the presentinvention incorporated into an electric detonator;

FIG. 6 is a cross-sectional view of the primer capsule of the presentinvention incorporated into a non-electric detonator; and

FIG. 7 is a cross-sectional view of the primer capsule of the presentinvention.

DESCRIPTION OF THE INVENTION

The invention relates to electric and non-electric detonators forexplosives. Specifically, the invention relates to detonators having aprimer capsule inserted therein. The primer capsule of the presentinvention is illustrated in FIGS. 1 and 2. Referring to FIG. 1, primercapsule 1 is comprised of top 2 and bottom 3 having hollow channel 4running therethrough. Top 2 has a small opening 5. As shown, channel 4is in communication with opening 5 in top 2. Preferably, top 2 ispointed or frustrum-shaped and bottom 3 is tubular-shaped. As usedherein, frustrum-shaped means shaped like the part of a cone or pyramidthat is formed by cutting off the top by a plane parallel to the base.Preferably, channel 4 in top 2 and for a portion in bottom 3 isfrustro-conical or frustro-trapezoidal-shaped. Preferably, the remainingportion of channel 4 in bottom 3 which is not frustro-conical orfrustro-trapezoidal-shaped is tubular-shaped or cylindrical. Bottom 3has a large opening 6 in communication with channel 4 as shown inFIG. 1. Large opening 6 is provided so that channel 4 can be in directcontact with an external base charge to be detonated. Preferably, thelarge opening is of the same width as channel 4 in bottom 3. FIG. 2 is aperspective view of primer capsule 1 shown in cross-section in FIG. 1.

The primer capsule of the present invention is preferably of a singleuniform construction whereby the top and bottom are constructed of thesame material or materials. Examples of materials which may be used toconstruct the primer capsule of the present invention include, but arenot limited to, steel, lead, copper and copper alloys, aluminum, zinc,thermoplastic resins, graphite, or the like and mixtures thereof.

The dimensions of top 2, bottom 3, channel 4, opening 5, opening 6 andgenerally, primer capsule 1 is dependent upon the desired applicationand use of the primer capsule. Generally, the primer capsule of thepresent invention is of such shape and construction wherein it can beeasily inserted into a detonator shell to provide intimate contact orcommunication between the core of a delay element in the detonator shellwith a primer charge contained in the primer capsule through opening 5in top 2 of capsule 1. However, it is also contemplated that primercapsule 1 of the present invention may be used alone, i.e., not insertedinto a detonator.

FIG. 3 illustrates a loaded primer capsule 1 of the present invention.Referring to FIG. 3, a primer charge material 7 is contained within thefrustro-conical shaped portion of channel 4 in top 2 and bottom 3. Asmall amount of base charge material 8 is contained in channel 4 ofbottom 3 and is pressed directly against primer charge 7 in channel 4.

The primer charge material contained inside the top of the primercapsule can be comprised of any primer charge material known in the artand includes, but is not limited to, lead azide, lead styphnate,diazodinitrophenol, and lead azide/lead styphnate mixtures. The specificprimer charge material and the amount utilized depends upon theapplication, the desired rate of detonation, and the base charge to beinitiated.

The small amount of base charge material 8 used in the present inventionmay be comprised of any known base charge material and includes, but isnot limited to, such materials as PETN, RDX, HMX, or tetryl or mixturesthereof. The specific base charge material used and the amount useddepends on the application, desired rate of detonation, and the basecharge to be detonated.

Referring to FIG. 3, portion 9 of the walls of primer capsule 1surrounding the frustro-conical portion of channel 4 containing primercharge 7 in top 2 and bottom 3 is thicker than the walls surrounding thetubular portion of channel 4 containing base charge material 8 in bottom3. Portion 9 of the walls are of sufficient thickness to provideprotection of primer charge 7 contained therein such that the primercharge material is not susceptible to sympathetic initiation fromexternal sources. However, it is contemplated that other means ofprotection can be used instead of thicker walls. For example, portion 9of the walls can be constructed of various materials which provideincreased protection of the primer charge from sympathetic initiation.

In addition to the protective top, the primer charge is also protectedfrom sympathetic detonation by the base charge material 8. The basecharge material 8 is less sensitive than primer charge 7. Preferably,the base charge material is pressed against the primer charge such thatthe primer charge 7 is protected against sympathetic initiation fromforces originating from the bottom of the primer capsule.

Channel 4 of primer capsule 1 is constructed such that upon initiationof the primer charge by a delay element through opening 5, the primercharge material reaches full velocity and shock and its output isfocused upon base charge material 8 whereby efficient initiation of anexternal base charge is obtained. Note, while a portion of channel 4 maybe frustro-conical shaped it may also be frustro-trapezoidal shaped.

While the drawings illustrate primer capsule 1 having a portion ofchannel 4 frustro-conical shaped, it should be understood that channel 4may also be frustro-conical shaped or frustro-trapezoidal shapedthroughout the entire length of primer capsule 1, i.e., from opening 5in top 2 to the end of tubular bottom 3. In addition, though the presentinvention has been illustrated and described wherein the frustro-conicalshaped portion of channel 4 contains only primer charge material, it isunderstood and contemplated that some primer charge material may becontained in the tubular shaped portion of channel 4 in bottom 3 and/orsome of the base charge material may be contained within thefrustro-conical shaped portion of channel 4 in top 2 or both.

The performance of the primer capsule of the present invention asopposed to a primer system wherein the primer charge is not protectednor is the output of the primer charge focused toward the base charge isillustrated in Table I below:

                  TABLE I                                                         ______________________________________                                        Detonator Explosive Output                                                                      Base Charge Grams of                                        Primer System     Weight      Sand Crushed                                    ______________________________________                                        120 mg. lead azide on top of                                                                    780 mg. PETN                                                                              106                                             base charge, no confinement and                                               no focusing                                                                   100 mg. lead azide plus 50 mg.                                                                  600 mg. PETN                                                                              104                                             PETN inside primer capsule                                                    ______________________________________                                    

From the data in Table I, the primer capsule of the present inventiongenerated 0.160 grams crushed sand per milligram of PETN, while theunconfined system generated only 0.136 grams crushed sand per milligramof PETN. The primer capsule of the present invention generated thisadditional output using approximately 16 percent less lead azide.

The data in Table II below illustrates the higher level of shockprotection provided by the primer capsule of the present invention.Detonators containing primer capsules of the present invention cantherefore withstand much higher shock pressures in boreholes withoutsympathetic initiation.

                  TABLE II                                                        ______________________________________                                        Resistance to Underwater Propagation                                          Primer System       Pressure Tolerance                                        ______________________________________                                        No confinement and no focusing                                                                    8,000-9,000 psi                                           Primer capsule of the present                                                                     14,000-16,000 psi                                         invention                                                                     ______________________________________                                    

FIG. 4 illustrates the primer capsule of the present invention insertedinto detonator shell 10 containing delay element 11 having a core 12centrally located therein. The detonator primer capsule is inserted intoone end of the detonator shell such that opening 5 in top 2 containingprimer charge material. 7 is in direct contact with core 12 of delayelement 11 which is inserted in the other end of the detonator shell. Asshown also in FIG. 3 and described above, in the primer capsule of thepresent invention, primer charge material 7 is in direct contact withbase charge material 8.

Detonator shell 10 as illustrated and described above, may be comprisedof various materials known in the art and includes, but is not limitedto, steel, lead, aluminum, copper, thermoplastic resins, graphite, andthe like and mixtures thereof. Preferably, the detonator shell is oftubular construction.

Referring to FIG. 5, an electric detonator is shown utilizing the primercapsule of the present invention. As shown in FIG. 5, delay element 11is inserted in one end of detonator shell 10 and primer capsule 1 isinserted into the other end of detonator 10 as shown and described inFIG. 4. An electric ignition source 14 is provided in air space 15. Airspace 15 containing the ignition source 14 is provided with a plasticinsulator sleeve 16. The ignition source 14 inside air space 15 issecured inside detonator shell 10 by sealing plug 17. Through sealingplug 17 run leg wires 18 which connect to ignition source 14 and to anexternal electrical source for ignition.

Primer capsule 1 of the present invention can be used in a non-electricdetonator as shown in FIG. 6. Delay element 11 and primer capsule 1 areinserted into detonation shell 10 as shown in FIGS. 4 and 5 anddescribed above. As shown in FIG. 6, a static separator 19 is providedabove delay element 11. On top of the static separator 19 is provided aclosure bushing 20 having a channel running therethrough containingnon-electric signal tube 21.

FIG. 7 illustrates one embodiment of the primer capsule of the presentinvention wherein channel 4 is frustro-conical or frustro-trapezoidalshaped for its entire length.

While the illustrative embodiments of the invention have been describedwith particularity, it will be understood that various othermodifications will be apparent to and can be readily made by thoseskilled in the art without departing from the spirit and scope of theinvention. Accordingly, it is not intended that the scope of claimsappended hereto be limited to the examples and descriptions set forthherein but rather that the claims be construed as encompassing all thefeatures of patentable novelty which reside in the present invention,including all features which would be treated as equivalents thereof bythose skilled in the art to which the invention pertains.

What is claimed is:
 1. A primer capsule for incorporation into adetonator comprising:a pointed top having a frustro-conical orfrustro-trapezoidal-shaped channel containing primer charge; a tubularbottom having a channel containing primer charge and base chargematerial; said top having a small opening in communication with thechannel containing primer charge; said bottom attached to said topwhereby the channels in the top and bottom are in communication so thatthe primer charge in the top and primer charge in the bottom are incontact.
 2. The primer capsule of claim 1 wherein the top and bottom arecomprised of steel, lead, zinc, copper and copper alloys, aluminum,graphite, the thermoplastic resins, or mixtures or derivatives thereof.3. The primer capsule of claim 1 wherein the primer charge is comprisedof lead azide, lead styphnate, diazodinitrophenol, or mixtures thereof.4. The primer capsule of claim 1 wherein the base charge material iscomprised of PETN, tetryl, RDX, HMX or mixtures thereof.
 5. The primercapsule of claim 1 wherein the top and bottom are comprised of a singleuniform construction.
 6. The primer capsule of claim 1 wherein a portionof the channel in the tubular bottom containing primer charge and basecharge material is frustro-conical or frustro-trapezoidal-shaped.
 7. Theprimer capsule of claim 1 wherein a portion of the channel in thetubular bottom containing primer charge is frustro-conical orfrustro-trapezoidal-shaped and the portion of the channel containingbase charge material is tubular shaped.
 8. A primer capsule comprising:afrustrum top and a tubular bottom, said top comprised of first andsecond ends and having a frustro-conical or frustro-trapezoidal-shapedchannel containing primer charge, said first end of the top having acentrally located small opening in communication with the channelcontaining primer charge, said bottom having first and second ends andhaving a channel containing primer charge and base charge material, saidfirst end of the bottom is attached to the second end of the top, suchthat the primer charge in the top and the primer charge in the bottomare in communication, said second end of the bottom having a largeopening.
 9. The primer capsule of claim 8 wherein the primer charge iscomprised of lead azide, lead styphnate, diazodinitrophenol, or mixturesthereof.
 10. The primer capsule of claim 8 wherein the base chargematerial is comprised of PETN, tetryl, RDX, or HMX or mixtures thereof.11. The primer capsule of claim 8 wherein the top and bottom arecomprised of steel, lead, zinc, copper and copper alloys, aluminum,graphite, thermoplastic resins, or mixtures or derivatives thereof. 12.The primer capsule of claim 8 comprised of a single uniformconstruction.
 13. The primer capsule of claim 8 wherein the channel inthe bottom containing primer charge is frustro-conical orfrustro-trapezoidal shaped.
 14. The primer capsule of claim 8 wherein aportion of the channel in the bottom containing base charge material istubular shaped.
 15. The primer capsule of claim 8 wherein a portion ofthe channel in the bottom containing base charge material is tubularshaped and a portion of the channel in the bottom containing primercharge is frustro-conical or frustro-trapezoidal shaped.
 16. A primercapsule for incorporation into a detonator comprising:a protectivefrustrum top having a frustro-conical-shaped channel containing primercharge and a tubular bottom having a channel containing primer chargeand a small amount of base charge material, the frustrum top has firstand second ends and has a small opening in the first end incommunication with the channel containing primer charge, said tubularbottom has first and second ends and said first end of the bottom isconnected to said second end of the top such that the channels of thetop and bottom are in communication.
 17. The primer capsule of claim 16wherein the top and bottom are comprised of steel, lead, zinc, copperand copper alloys, aluminum, graphite, thermoplastic resins, or mixturesor derivatives thereof.
 18. The primer capsule of claim 16 wherein theprimer charge is comprised of lead azide, lead styphnate,diazodinitrophenol, or mixtures thereof.
 19. The primer capsule of claim16 wherein the small charge of base material is PETN, tetryl, RDX, HMXor mixtures thereof.
 20. The primer capsule of claim 16 comprised of asingle uniform construction.
 21. The primer capsule of claim 16 whereinthe channel in the bottom containing primer charge and a small amount ofbase charge material is frustro-conical or frustro-trapezoidal shaped.22. The primer capsule of claim 16 wherein the channel containing primercharge and a small amount of base charge material in the tubular bottomis cylindrical.
 23. The primer capsule of claim 16 wherein a portion ofthe channel in the bottom is frustro-conical or frustro-trapezoidalshaped and a portion is tubular shaped.
 24. A detonator comprising:atubular shell having first and second ends containing a delay elementand a primer capsule; said delay element being positioned inside thefirst end of the shell and having a core centrally located therein; saidprimer capsule being positioned inside the second end of the shell andcomprised of a protective frustrum-shaped top and a tubular bottom; saidtop having first and second ends with a frustro-conical orfrustro-trapezoidal channel containing primer charge; said top having anopening centrally located in the first end in communication with thechannel containing primer charge; said tubular bottom comprised of firstand second ends and having a channel containing a primer charge and basecharge material; said first end of the bottom being connected to saidsecond end of the top such that the primer charge in the top and theprimer charge in the bottom are contacted; said primer capsule ispositioned inside the second end of the shell such that the openingcentrally located in the first end of the top is in communication withthe delay element core.
 25. The detonator of claim 24 wherein the primercapsule top and bottom are comprised of steel, lead, zinc, copper andcopper alloys, aluminum, graphite, thermoplastic resins, or mixtures orderivatives thereof.
 26. The detonator of claim 24 wherein the primercharge is comprised of lead azide, lead styphnate, diazodinitrophenol,or mixtures thereof.
 27. The detonator of claim 24 wherein the smallcharge of base material is PETN, tetryl, RDX, HMX or mixtures thereof.28. The detonator of claim 24 wherein the primer capsule is comprised ofa single uniform construction.
 29. The detonator of claim 24 wherein thechannel in the bottom of the primer capsule containing primer charge isfrustro-conical or frustro-trapezoidal shaped.
 30. The detonator ofclaim 24 wherein a portion of the channel in the bottom of the primercapsule is cylindrical.
 31. The detonator of claim 24 wherein a portionof the channel in the: bottom of the primer capsule is frustro-conicalor frustro-trapezoidal shaped and a portion of the channel in the bottomis cylindrical.
 32. A primer capsule comprising:a frustrum top havingfirst and second ends and a tubular bottom having first and second ends;said top having a frustro-conical-shaped channel containing primercharge; said first end of the top having a small opening incommunication with said channel containing primer charge; said secondend of the top having an opening the same width as the channel; saidbottom having a tubular-shaped channel containing primer charge and basecharge material; said bottom first and second ends having openings incommunication with the channel of the same width as the channelcontaining primer charge and base charge material; said bottom first endattached to said top second end such that the primer charge in the topand the primer charge in the bottom are contacted.
 33. The primercapsule of claim 32 wherein the top and bottom are comprised of steel,lead, zinc, copper and copper alloys, aluminum, graphite, thermoplasticresins, or mixtures or derivatives thereof.
 34. The primer capsule ofclaim 32 wherein the primer charge is comprised of lead azide, leadstyphnate, diazodinitrophenol, or mixtures thereof.
 35. The primercapsule of claim 32 wherein the base charge material is PETN, tetryl,RDX, HMX or mixtures thereof.
 36. The primer capsule of claim 32comprised of a single uniform construction.
 37. A primer capsulecomprised of:a protective pointed top and a tubular bottom having afrustro-conical or frustro-trapezoidal shaped channel runningtherethrough; said channel containing a primer charge and base chargematerial; said top having a small opening in communication with thechannel; and said bottom having a large opening in communication withthe channel.
 38. The primer capsule of claim 37 wherein the top andbottom are comprised of steel, lead, zinc, copper and copper alloys,aluminum, graphite, thermoplastic resins, or mixtures or derivativesthereof.
 39. The primer capsule of claim 37 wherein the primer charge iscomprised of lead azide, lead styphnate, diazodinitrophenol, or mixturesthereof.
 40. The primer capsule of claim 37 wherein the base chargematerial is PETN, tetryl, RDX, HMX or mixtures thereof.
 41. The primercapsule of claim 37 comprised of a single uniform construction.